I'd say that the Dev App is a great place for these kind of suggestions. Right now the light flak is being looked at, and last patch the artemis was being adjusted.
Light Flak - Personally I think it's fairly ok, despite the poor arming time and limited range compared to similar guns. It often gets overlooked because the guns it can pair with often do better paired with something else. The hades/artemis have a better range than a hades/flak, where gat/mortar has more damage potential and can do well up close; where the gat flak has to stay at a very specific range (too far and the gat can't hit, too close and the flak doesn't arm)
However, it is being looked at currently.
Banshee- This has always been one of my least used guns. It's not bad, it's just not my style. It has a long range and good arcs, but relies more on starting fires than raw damage. I've used it effectively and seen it used effectively, it's just not as mainstream as other pure explosive weapons.
artemis- This was recently nerfed a little in terms of turning speed and shell velocity. It's still a powerful gun, but is harder to use on moving targets due to the turning speed and slower shell. You have to lead them more and it's a little more difficult to hit the components. Although a good gunner can use it just as effectively. Overall it's pretty powerful at disabling, and can even be used as a finisher. I believe it also can start some fires, which can add to armor removal (not sure what the fire % is )
Hades - To me this gun is alarmingly powerful. It's great against most aspects of the ship, and has a high chance of starting fires. The arming time isn't all that long, and it covers a large range. It is fairly difficult to hit with, but again, with a good gunner it's incredibly powerful. It's one of the guns that can be used by itself (or used with another hades) to extreme effect, since it can break the armor and destroy the hull; along with the balloon and all the fire it causes.
Heavy flak- The heavy flak is actually quite powerful. Ideally you want to pair it with something to break the armor, otherwise you're not doing much. It does have a pretty good chance to start a fire, which combined with the raw damage and the engineer cooldowns can actually take down the armor (although slowly).
The other heavy guns also need to be paired. The carronade and lumberjack can generally be used solo, but then they often use the terrain for that extra damage, and rely on keeping the enemy in a position where they can't counterattack. It's far from a fast kill.
The hwacha is in the same boat as the flak, although it relies more on disabling. By itself, and with it's long reload, it's hard for it to actually break the armor and then damage the hull. It usually relies on keeping the enemy busy putting out the fires and rebuilding all the other components, and hoping they neglect the hull long enough. Overall it's another slow kill by itself.